Even if the mileage doesn't quite match, don't forget the extra power you get with the new 6.7 PSD and you are right about the weight. Like you said these trucks are bigger and have to face emissions. I wonder how different these trucks would be if the automakers didn't have start to dealing with the strict emissions standards the EPA started enacting almost ten years ago. I'm tempted to believe that the fuel efficiency would be much greater today and they would not even have the same engines. Emissions is a huge influence on how these trucks are built.